Definitely rest longer than 90 seconds. Doing sets across, I usually rest the same number of minutes as the number of reps - 5 minutes per set for 5x5, 3 minutes per for 8x3, etc. Max sets, I usually rest however long I need to to make the reps. As I get closer to competition, I usually cut the rest down to 2 minutes per set - I want to be ready to follow myself on the platform if need be.